/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.classfile.util;

import proguard.classfile.ClassConstants;

/**
 * An <code>InternalTypeEnumeration</code> provides an enumeration of all types listed in a given internal descriptor or
 * signature of a class, a method, or a field.
 *
 * The leading formal type parameters, if any, can be retrieved separately.
 *
 * The return type of a method descriptor can also be retrieved separately.
 *
 * @author Eric Lafortune
 */
public class InternalTypeEnumeration {
    private String descriptor;
    private int formalTypeParametersIndex;
    private int openIndex;
    private int closeIndex;
    private int index;

    /**
     * Creates a new InternalTypeEnumeration for the given method descriptor.
     */
    public InternalTypeEnumeration(String descriptor) {
        this.descriptor = descriptor;

        // Find any formal type parameters.
        if (descriptor.charAt(0) == ClassConstants.TYPE_GENERIC_START) {
            formalTypeParametersIndex = 1;

            int nestingLevel = 1;
            do {
                char c = descriptor.charAt(formalTypeParametersIndex++);
                switch (c) {
                    case ClassConstants.TYPE_GENERIC_START: {
                        nestingLevel++;
                        break;
                    }
                    case ClassConstants.TYPE_GENERIC_END: {
                        nestingLevel--;
                        break;
                    }
                }
            } while (nestingLevel > 0);
        }

        this.openIndex = descriptor.indexOf(ClassConstants.METHOD_ARGUMENTS_OPEN, formalTypeParametersIndex);

        this.closeIndex =
            openIndex >= 0 ? descriptor.indexOf(ClassConstants.METHOD_ARGUMENTS_CLOSE, openIndex) : descriptor.length();

        this.index = openIndex >= 0 ? openIndex + 1 : formalTypeParametersIndex;
    }

    /**
     * Returns whether the descriptor has leading formal type parameters.
     */
    public boolean hasFormalTypeParameters() {
        return formalTypeParametersIndex > 0;
    }

    /**
     * Returns the leading formal type parameters from the descriptor.
     */
    public String formalTypeParameters() {
        return descriptor.substring(0, formalTypeParametersIndex);
    }

    /**
     * Returns whether the descriptor is a method signature.
     */
    public boolean isMethodSignature() {
        return openIndex >= 0;
    }

    /**
     * Returns whether the enumeration can provide more types from the method descriptor.
     */
    public boolean hasMoreTypes() {
        return index < closeIndex;
    }

    /**
     * Returns the next type from the method descriptor.
     */
    public String nextType() {
        int startIndex = index;

        skipArray();

        char c = descriptor.charAt(index++);
        switch (c) {
            case ClassConstants.TYPE_CLASS_START:
            case ClassConstants.TYPE_GENERIC_VARIABLE_START: {
                skipClass();
                break;
            }
            case ClassConstants.TYPE_GENERIC_START: {
                skipGeneric();
                break;
            }
        }

        return descriptor.substring(startIndex, index);
    }

    /**
     * Returns the return type from the descriptor, assuming it's a method descriptor.
     */
    public String returnType() {
        return descriptor.substring(closeIndex + 1);
    }

    // Small utility methods.

    private void skipArray() {
        while (descriptor.charAt(index) == ClassConstants.TYPE_ARRAY) {
            index++;
        }
    }

    private void skipClass() {
        while (true) {
            char c = descriptor.charAt(index++);
            switch (c) {
                case ClassConstants.TYPE_GENERIC_START:
                    skipGeneric();
                    break;

                case ClassConstants.TYPE_CLASS_END:
                    return;
            }
        }
    }

    private void skipGeneric() {
        int nestingLevel = 1;

        do {
            char c = descriptor.charAt(index++);
            switch (c) {
                case ClassConstants.TYPE_GENERIC_START:
                    nestingLevel++;
                    break;

                case ClassConstants.TYPE_GENERIC_END:
                    nestingLevel--;
                    break;
            }
        } while (nestingLevel > 0);
    }

    /**
     * A main method for testing the type enumeration.
     */
    public static void main(String[] args) {
        try {
            for (int index = 0; index < args.length; index++) {
                String descriptor = args[index];

                System.out.println("Descriptor [" + descriptor + "]");
                InternalTypeEnumeration enumeration = new InternalTypeEnumeration(descriptor);

                if (enumeration.hasFormalTypeParameters()) {
                    System.out.println("  Formal type parameters [" + enumeration.formalTypeParameters() + "]");
                }

                while (enumeration.hasMoreTypes()) {
                    System.out.println("  Type [" + enumeration.nextType() + "]");
                }

                if (enumeration.isMethodSignature()) {
                    System.out.println("  Return type [" + enumeration.returnType() + "]");
                }
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
}
